Control systems for drive systems and work elements of power machines

ABSTRACT

Systems and methods for power machine drive control are provided. The drive control system can include a foot input and a hand input in an operator station of a compact tractor that can each be configured to independently provide forward and reverse (or other) drive commands. In addition, a hydraulic control systems and methods for work element operations of a power machine are provided. Functions of an implement can be configured to operate based on inputs from a dual-axis joystick. The dual-axis control over an implement provides a first function (e.g., a lift function) to remain in a float configuration while allowing the operator to command a second function (e.g., a tilt function).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and hereby incorporates by reference, U.S. Provisional Patent Application No. 63/310,459, filed Feb. 15, 2022.

BACKGROUND

This disclosure is directed toward power machines. More particularly, this disclosure is directed towards input systems and methods for controlling hydraulic functions of a power machine, including hydraulic or hydrostatic drive and operation of hydraulically powered workgroups (e.g., lift arms and associated actuators) as well as hydraulic power implements that may be operably coupled to the power machine. Power machines, for the purposes of this disclosure, include any type of machine that generates power to accomplish a particular task or a variety of tasks. One type of power machine is a work vehicle. Work vehicles are generally self-propelled vehicles that have a work device, such as a lift arm (although some work vehicles can have other work devices) that can be manipulated to perform a work function. Work vehicles include loaders (including mini-loaders), excavators, utility vehicles, mowers, tractors (including compact tractors), and trenchers, to name a few examples.

The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.

SUMMARY

Some examples of the disclosed technology can provide improved control for drive systems and work elements of power machines, including relative to drive commands provided at independently operable input devices and relative to operation of work elements in a float mode.

Some examples provide a power machine that includes a power source and drive motors operably coupled to the power source and to tractive elements of the power machine to power drive operations of the power machine. A first drive input device can be configured to provide a first control signal to selectively power operation of the drive motors for travel in a forward direction or a reverse direction. A second drive input device can be configured to provide a second control signal to selectively power operation of the drive motors for travel in the forward or the reverse direction. The first drive input device can be independently movable relative to the second drive input device to provide the first control signal and the second drive input device can be independently movable relative to the first drive input device to provide the second control signal.

In some examples, the drive motors can be hydraulically powered drive motors, and a drive pump can be operably coupled to the power source and can be configured to power the drive motors to selectively drive the power machine in the forward direction or the reverse direction. The first drive input device can be configured to provide the first control signal to control the drive pump to selectively power operation of the drive motors for travel in the forward direction or the reverse direction. The second drive input device can be configured to provide the second control signal to control the drive pump to selectively power operation of the drive motors for travel in the forward or the reverse direction.

In some examples, the first drive input device can include a single-axis joystick.

In some examples, the second drive input device can include at least one foot pedal.

In some examples, the first drive input device and the second drive input device can be in hydraulic communication with a hydraulically operated control device arranged to provide pilot-operated control of displacement of a drive pump using hydraulic pressure within a drive control hydraulic circuit. The drive control hydraulic circuit can include a first control path that can include a first shuttle valve between the hydraulically operated control device and a first outlet port of each of the first and second drive input devices. First inlets of the first shuttle valve can be in hydraulic communication with the first outlet ports, and a first outlet of the first shuttle valve can be in hydraulic communication with the hydraulically operated control device to provide a first pilot control signal to the hydraulically operated control device. The drive control hydraulic circuit can include a second control path that can include a second shuttle valve between the hydraulically operated control device and a second outlet port of each of the first and second drive input devices. Second inlets of the second shuttle valve can be in hydraulic communication with the second outlet ports, and a second outlet of the second shuttle valve can be in hydraulic communication with the hydraulically operated control device to provide a second pilot control signal to the hydraulically operated control device opposed to the first pilot control signal.

Some examples can provide a hydraulic control circuit for a drive system of a power machine. A first drive input device can be in communication with a pilot pressure source. The first drive input device can be configured to receive a first operator input relative to a first degree of freedom and to selectively provide, based on the first operator input, a first pilot signal along first control path or along a second control path to command, respectively, operation of a drive motor of the drive system in a forward direction or a reverse direction. A second drive input device can be in communication with a pilot pressure source. The second drive input device can be configured to receive a second operator input relative to a second degree of freedom and to selectively provide, based on the second operator input, a second pilot signal along the first control path or along the second control path to command, respectively, operation of the drive motor of the drive system in the forward direction or the reverse direction. A pilot-operated actuator can be configured to control a displacement of the drive motor based on pilot signals from the first and second control paths.

In some examples, a first shuttle valve can be arranged along the first control path between the pilot-operated actuator and the first and second drive input devices. A second shuttle valve can be arranged along the second control path between the pilot-operated actuator and the first and second drive input devices.

In some examples, the first drive input device can include a joystick and the second drive input device can include a pedal.

Some examples provide a power machine that includes a power source, and a work element configured to be powered by the power source for work operations. An implement interface can be configured to removably, operably couple an implement to the power machine. At least one power coupler can be configured to transmit power from the power machine to the implement when the implement is removably, operably coupled to the implement interface. The power machine can further include a dual-axis joystick. Movement of the dual-axis joystick along a first axis can actuate a first actuator configured for a first work function. Movement of the dual-axis joystick along a second axis can actuate a second actuator of the implement that can be powered via the at least one power coupler for a second work function of the implement. The dual-axis joystick being positioned at a first threshold position along the first axis can place the first actuator in a float configuration for the first work function. The dual-axis joystick being positioned at a second threshold position along the second axis can place the second actuator in a float configuration for the second work function.

In some examples, an auxiliary pump can be operably coupled to the power source and can be configured to pressurize a work actuator circuit that can include the first actuator. At least one power coupler can be configured to place the implement in fluid communication with the work actuator circuit to transmit hydraulic power from the power machine to the implement. The dual-axis joystick can be operably coupled to a first hydraulic control spool and a second hydraulic control spool. Movement of the dual-axis joystick along the first axis can adjust a position of the first hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to actuate the first actuator. Movement of the dual-axis joystick along the second axis can adjust a position of the second hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to the at least one power coupler for actuation of the second actuator. When the dual-axis joystick is positioned at the first threshold position along the first axis, the first hydraulic control spool can be positioned to place the first actuator in the float configuration for the first work function. When the dual-axis joystick is positioned at the second threshold position along the second axis, the second hydraulic control spool can be positioned to place the second actuator in the float configuration for the second work function.

In some examples, a switch can be in communication with a control system of the power machine, The switch can be arranged to be actuated by movement of the dual-axis joystick to a third threshold position along the first axis. Upon actuation of the switch, the control system can be configured to implement a float assist mode in which the auxiliary pump provides pressurized flow in the work actuator circuit to resist but not stop movement of the first actuator under external loads (e.g., from gravity).

In some examples, the first threshold position can be different from the second threshold position.

In some examples, a first solenoid valve can be arranged on a first side of the first actuator and a second solenoid valve on a second side of the first actuator. Actuation of the switch can command control of the first and second solenoid valves to implement the float assist mode. The first and second solenoid valves can be configured to remove the first actuator from fluid communication with the first hydraulic control spool.

In some examples, when the switch is actuated, the first solenoid valve can place the first side of the first actuator in fluid communication with an adjustable pressure relief valve configured to adjust a pressure delivered to the first side of the first actuator by the auxiliary pump.

In some examples, a bracket can be coupled to the dual-axis joystick and can be configured to engage a switch to implement a float assist mode when the dual-axis joystick is positioned at a maximum end position along the first axis, across a range of positions along the second axis.

In some examples, the bracket can extend along the second axis such that the bracket maintains contact with the switch during movement of the dual-axis joystick along the second axis within the range of positions along the second axis.

Some examples provide a power machine assembly that can include a power machine and an implement that is operably coupled to an implement interface of the power machine and to at least one power coupler of the power machine.

Some examples provide a power machine that includes a power source, and a hydraulic pump operably coupled to the power source and configured to pressurize a work actuator circuit. A work element can be configured to be powered by the hydraulic pump for work operations. A switch can be in communication with a control system of the power machine that also includes a dual-axis joystick. Movement of the dual-axis joystick along a first axis can selectively provide pressurized fluid from the hydraulic pump to actuate a first actuator configured for a first work function. Movement of the dual-axis joystick along a second axis can selectively provide pressurized fluid from the hydraulic pump to actuate a second actuator configured for a second work function. When the dual-axis joystick is positioned at a first threshold position along the first axis, the dual-axis joystick actuates the switch to place the first actuator in a float configuration for the first work function. Upon actuation of the switch, the control system can be configured to implement a float assist mode in which the hydraulic pump provides pressurized flow in the work actuator circuit to resist but not stop movement of the first actuator under external loads.

In some examples, the dual-axis joystick can be operably coupled to a first hydraulic control spool and a second hydraulic control spool. Movement of the dual-axis joystick along the first axis can adjust a position of the first hydraulic control spool to selectively actuate the first actuator. Movement of the dual-axis joystick along the second axis can adjust a position of the second hydraulic control spool to selectively actuate the second actuator. When the dual-axis joystick is positioned at the first threshold position along the first axis, the dual-axis joystick can position the first hydraulic control spool to place the first actuator in the float configuration.

In some examples, the hydraulic pump can be an auxiliary pump.

Some examples provide a power machine that includes a power source, a work element, and an implement interface configured for operably coupling a removable implement to the power machine. An auxiliary pump can be operably coupled to the power source and can be configured to pressurize a work actuator circuit. The work actuator circuit can include: a first actuator arranged to be powered by the auxiliary pump to power work operations with the work element; and at least one power coupler configured to selectively provide pressurized fluid to the removable implement when the removable implement is operably coupled to the at least one power coupler. A dual-axis joystick can be operably coupled to a first hydraulic control spool and a second hydraulic control spool. Movement of the dual-axis joystick along a first axis can adjust a position of the first hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to actuate the first actuator. Movement of the dual-axis joystick along a second axis can adjust a position of the second hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to the at least one power coupler for actuation of a second actuator arranged on the removable implement.

This Summary and the Abstract can be provided to introduce a selection of concepts in a simplified form that can be further described below in the Detailed Description. This Summary can be not intended to identify key features or essential features of the claimed subject matter, nor can be they intended to be used as an aid in determining the scope of the claimed subject matter.

DRAWINGS

The following drawings are provided to help illustrate various features of non-limiting examples of the disclosure and are not intended to limit the scope of the disclosure or exclude alternative implementations.

FIG. 1 is a block diagram illustrating functional systems of a representative power machine on which examples of the present disclosure can be advantageously practiced.

FIG. 2 illustrates a perspective view of a representative power machine in the form of a compact tractor of the type on which the disclosed examples can be practiced.

FIG. 3 is a block diagram illustrating components of a power system of a tractor such as the compact tractor illustrated in FIG. 2 .

FIG. 4 is a perspective view of an example configuration of the compact tractor of FIG. 2 , including operator control devices for a hydraulic drive system the compact tractor.

FIG. 5 is a hydraulic schematic of the hydraulic drive system of FIG. 4 .

FIG. 6 is a perspective partial view of a control device configured as a two-axis joystick for control of the work elements of the compact tractor of FIG. 2 .

FIG. 7 is a hydraulic schematic of a work actuator hydraulic circuit under control of the control device of FIG. 6 .

DETAILED DESCRIPTION

The concepts disclosed in this discussion are described and illustrated by referring to exemplary configurations. These concepts, however, are not limited in their application to the details of construction and the arrangement of components in the illustrative examples and are capable of being practiced or being carried out in various other ways. The terminology in this document is used for the purpose of description and should not be regarded as limiting. Words such as “including,” “comprising,” and “having” and variations thereof as used herein are meant to encompass the items listed thereafter, equivalents thereof, as well as additional items.

Conventional power machines can include one or more control devices for controlling the drive functions (e.g., forward or reverse functions) of the respective power machine. For example, conventional examples have included a lever as a first input and a foot pedal as a second input, with the first and second inputs mechanically attached to one another such that movement of the lever results in movement of the foot pedal (and vice versa). During some operations, this arrangement may not allow for refined control of the drive functions of the power machine.

In addition, conventional power machines can include separate control devices for controlling primary (e.g., lift arm) and auxiliary hydraulic functions. For example, conventional examples can include a first lever for controlling a primary function and a second lever for controlling an auxiliary function. This arrangement can clutter the control panel of a power machine with the inclusion of multiple levers and result in an unrefined or non-intuitive machine control experience for an operator, as well as complicate execution of certain work functions.

Examples of the disclosed technology can address one or more of the issues noted above, including as part of an improved control system for drive or workgroup functions for a compact tractor. In some examples, a hydraulic control system for drive operations of a compact tractor can be configured to operate based on separate independent inputs with overlapping command architecture. For example, a first user (e.g., foot) operated input device and a second user (e.g., hand) operated input device in an operator station of a compact tractor can each be configured to independently provide the same type of directional (i.e., forward and reverse) or speed-related drive commands. A hydraulic, electronic, or other control circuit operated by the foot- and hand-operated input devices can be configured to controllably power drive operations at one or more drive motors based on a combination of the drive commands (e.g., via a summation of the commands, with or without differential gain, or via control of drive motors based on a dominant input signal). Thus, operators can selectively provide inputs at one or both input devices to separately or cooperatively control drive operations.

Some control systems can be configured to implement this type of control using generally known hydraulic components. For example, a first shuttle valve can be interposed between a forward-drive pilot line of each of the foot-operated input device (e.g., a drive pedal) and the hand-operated input device (e.g., a drive lever or joystick) and a pilot-controlled actuator to control drive pump displacement. A second shuttle valve can be interposed between a reverse-drive pilot line of each of the foot-operated input device and the hand-operated input device and the pilot-controlled actuator. Thus, for example, the foot-operated input device and the hand-operated input device can be operated independently, with actual drive operations for same-direction input commands being implemented based on the strongest input signal.

In some examples, a similar architecture as described herein relative to hydraulic control can be implemented relative to electronic control inputs or control of electronic drive actuators. Thus, in some cases, independent user inputs at electronic input devices can independently signal an electronic control system to command drive operations relative to the same degrees of freedom (e.g., inputs at touchscreens or pads, electronic joysticks or levers, keypads, etc. can indicate the same type of directional or speed-related drive commands). An electronic control system can then controllably power drive operations at one or more electronic drive motors based on a combination of overlapping user inputs at different input interfaces.

In this regard, generally, discussion of particular hydraulic examples herein should be understood to apply equally to electronic systems, with electronic hardware or software modules as generally known in the art configured to operate in place of the hydraulic input, transmission, processing, and output components as discussed. Thus, relative to the example above, known software or electronic modules (e.g., various types of sensors) can be arranged to receive electronic control inputs from independent user inputs (e.g., hand and foot devices) and implement drive control based on a dominant of the control inputs (e.g., control direction or speed based on a strongest of two inputs).

In some examples, multiple functions of a hydraulic control system for work element operations of a compact tractor (e.g., lift and tilt functions of an implement) can be configured to operate based on inputs from a single dual-axis joystick. For example, inputs along a first axis of the joystick can be configured to provide lift (e.g., extend) or lower (e.g., retract) implement commands, and inputs along a second axis of the joystick can be configured to selectively control operation of an operably coupled implement (e.g., via control of flow of hydraulic fluid). In general, this dual-axis control over both a work element (e.g., a lift arm) and an attachable implement reduces the overall number of input devices needed to be operated by an operator.

For the purposes of this discussion, the term operably (or operatively) coupled indicates any coupling between an implement and a power machine that will result in power (e.g., pressurized hydraulic fluid, electrical power) and/or communication signals (fluidic, wired, or wireless electrical signals) being transmitted between the power machine and the implement. An implement that is operably coupled to a power machine can, but need not be, physically attached—e.g., rigidly or pivotally—to a frame or to a work element (e.g., a lift arm) of the power machine.

Hydraulic fluid flow (or electrical signals) to an operably coupled implement can control one or more hydraulic (or electrical) actuators on the implement. Exemplary actuators on attachments can be linear actuators (e.g., hydraulic cylinders), rotary actuators (e.g., hydraulic or electronic motors), or any other actuator capable of being actuated in response to the introduction of pressurized hydraulic fluid (or electrical current). In some cases, an operably coupled implement can be equipped with various flow (or current) directing devices to power more than one actuator on an implement (e.g., can be equipped with one or more valves to provide hydraulic flow to multiple hydraulic actuators).

In some examples, a joystick can be configured to allow a first function (e.g., a lift function) to remain in a float configuration while allowing the operator to actively command a second function (e.g., an implement function). Thus, for example, full functionality of a conventional two-lever control arrangement can be achieved with a single, dual-axis joystick, resulting in an improved control experience where an operator can simultaneously operate both the work element and the operably coupled implement with one movement.

These concepts can be practiced on various power machines, as will be described below. A representative power machine on which the examples of the disclosed technology can be practiced is illustrated in diagram form in FIG. 1 and one example of such a power machine is illustrated in FIGS. 2-3 and described below before any examples are disclosed. For the sake of brevity, only one power machine is illustrated and discussed as being a representative power machine. However, as mentioned above, the examples below can be practiced on any of a number of power machines, including power machines of different types from the representative power machine shown in FIGS. 2-3 . Power machines, for the purposes of this discussion, include a frame, at least one work element, and a power source that can provide power to the work element to accomplish a work task. One type of power machine is a self-propelled work vehicle. Self-propelled work vehicles are a class of power machines that include a frame, work element, and a power source that can provide power to the work element. At least one of the work elements is a motive system for moving the power machine under power.

FIG. 1 is a block diagram that illustrates the basic systems of a power machine 100, which can be any of a number of different types of power machines upon which the examples discussed below can be advantageously incorporated. The block diagram of FIG. 1 both identifies various systems on power machine 100 and shows relationships between various components and systems. At the most basic level, power machines for the purposes of this discussion include a frame, a power source, and a work element. The power machine 100 has a frame 110, a power source 120, and a work element 130. Because power machine 100 shown in FIG. 1 is a self-propelled work vehicle, it also has tractive elements 140, which are themselves work elements provided to selectively move the power machine over a support surface and an operator station 150 that provides an operating position where an operator can manipulate operator inputs for controlling the work elements of the power machine. A control system 160 is provided to interact with the other systems to perform various work tasks at least in part in response to control signals provided by an operator. For example, the control system 160 can be an integrated or distributed architecture of one or more processor devices and one or more memories that are collectively configured to receive operator input or other input signals (e.g., sensor data) and to output commands accordingly for power machine operations. According to other examples, the control system 160 can be a hydraulic circuit provided to interact with other systems to perform various work tasks at least in part in response to signals given by an operator by way of movement of input devices arranged on the power machine 100 (e.g., within the operator station 150).

Certain work vehicles have work elements that can perform a dedicated task. For example, some work vehicles have a lift arm to which various implements such as a bucket or a mower deck is attached such as by a pinning arrangement. The work element, i.e., the lift arm can be manipulated to position the implement to perform the task. The implement, in some instances can be positioned relative to the work element, such as by rotating a bucket relative to a lift arm, to further position the implement. In other instances, the bucket is not moveable with respect to the lift arm. In other words, some power machines do not have tilt cylinders of the type that can rotate a bucket relative to the lift arm. Under normal operation of such a work vehicle, the bucket is intended to be attached to the lift arm and under use. Such work vehicles may be able to accept other implements by disassembling the implement/work element combination and reassembling another implement in place of the original bucket. Other work vehicles, however, are intended to be used with a wide variety of implements and have an implement interface such as implement interface 170 shown in FIG. 1 . At its most basic, implement interface 170 is a connection mechanism between the frame 110 or a work element 130 and an implement, which can be as simple as a connection point for attaching an implement directly to the frame 110 or a work element 130 or more complex, as discussed below.

On some power machines, implement interface 170 can include an implement carrier, which is a physical structure movably attached to a work element. The implement carrier has engagement features and locking features to accept and secure any of a number of different implements to the work element. One characteristic of such an implement carrier is that once an implement is attached to it, it is fixed to the implement (i.e. not movable with respect to the implement) and when the implement carrier is moved with respect to the work element, the implement moves with the implement carrier. The term implement carrier as used herein is not merely a pivotal connection point, but rather a dedicated device specifically intended to accept and be secured to various different implements. The implement carrier itself is mountable to a work element 130 such as a lift arm or the frame 110. Implement interface 170 can also include one or more power sources for providing power to one or more work elements on an implement. Some power machines can have a plurality of work element with implement interfaces, each of which may, but need not, have an implement carrier for receiving implements. Some other power machines can have a work element with a plurality of implement interfaces so that a single work element can accept a plurality of implements simultaneously. Each of these implement interfaces can, but need not, have an implement carrier.

Frame 110 includes a physical structure that can support various other components that are attached thereto or positioned thereon. The frame 110 can include any number of individual components. Some power machines have frames that are rigid. That is, no part of the frame is movable with respect to another part of the frame. Other power machines have at least one portion that can move with respect to another portion of the frame. For example, excavators can have an upper frame portion that rotates with respect to a lower frame portion. Other work vehicles, including some compact tractors, have articulated frames such that one portion of the frame pivots with respect to another portion for accomplishing at least a portion of the machine movement related to steering functions.

Frame 110 supports the power source 120, which is configured to provide power to one or more work elements 130 including the one or more tractive elements 140, as well as, in some instances, providing power for use by an operably coupled implement via implement interface 170 (e.g., via one or more hydraulic connections on or near the implement interface 170). Power from the power source 120 can be provided directly to any of the work elements 130, tractive elements 140, and implement interfaces 170. Alternatively, power from the power source 120 can be provided to a control system 160, which in turn selectively provides power to the elements that capable of using it to perform a work function. Power sources for power machines typically include an engine such as an internal combustion engine and a power conversion system such as a mechanical transmission or a hydraulic system that is configured to convert the output from an engine into a form of power that is usable by a work element. Other types of power sources can be incorporated into power machines, including electrical sources or a combination of power sources, known generally as hybrid power sources.

FIG. 1 shows a single work element designated as work element 130, but various power machines can have any number of work elements. Work elements are typically attached to the frame of the power machine and movable with respect to the frame when performing a work task. In some examples, as also discussed above, work elements can include lift arm assemblies. In some examples, work elements can include mower decks or other similar equipment. In addition, tractive elements 140 are a special case of work element in that their work function is generally to move the power machine 100 over a support surface. Tractive elements 140 are shown separate from the work element 130 because many power machines have additional work elements besides tractive elements, although that is not always the case. Power machines can have any number of tractive elements, some or all of which can receive power from the power source 120 to propel the power machine 100. Tractive elements can be, for example, track assemblies, wheels attached to an axle, and the like. Tractive elements can be mounted to the frame such that movement of the tractive element is limited to rotation about an axle (so that steering is accomplished by a skidding action) or, alternatively, pivotally mounted to the frame to accomplish steering by pivoting the tractive element with respect to the frame.

Power machine 100 includes an operator station 150 that includes an operating position from which an operator can control operation of the power machine. In some power machines, the operator station 150 is defined by an enclosed or partially enclosed cab. Some power machines on which the disclosed technology may be practiced may not have a cab or an operator compartment of the type described above. For example, a walk behind loader may not have a cab or an operator compartment, but rather an operating position that serves as an operator station from which the power machine is properly operated. As another example, many compact tractors do not have a cab to enclose its operator station. More broadly, power machines other than work vehicles may have operator stations that are not necessarily similar to the operating positions and operator compartments referenced above. Further, some power machines such as power machine 100 and others, whether or not they have operator compartments or operator positions, may be capable of being operated remotely (i.e., from a remotely located operator station) instead of or in addition to an operator station adjacent or on the power machine. This can include applications where at least some of the operator-controlled functions of the power machine can be operated from an operating position associated with an implement that is coupled to the power machine. Alternatively, with some power machines, a remote-control device can be provided (i.e., remote from both of the power machine and any implement to which is it coupled) that is capable of controlling at least some of the operator-controlled functions on the power machine.

FIG. 2 illustrates a compact tractor 200, which is one particular example of a power machine of the type illustrated in FIG. 1 where the examples discussed below can be advantageously employed. To that end, features of the tractor 200 described below include reference numbers that are generally similar to those used in FIG. 1 . For example, the tractor 200 is described as having a frame 210, just as power machine 100 has a frame 110. The tractor 200 is described herein to provide a reference for understanding one environment on which the examples described below related to hydraulic drive and auxiliary hydraulic control systems and methods may be practiced. The tractor 200 should not be considered limiting especially as to the description of features that tractor 200 may have described herein that are not essential to the disclosed examples and thus may or may not be included in power machines other than the tractor 200 upon which the examples disclosed below may be advantageously practiced. Unless specifically noted otherwise, examples disclosed below can be practiced on a variety of power machines, with the tractor 200 being only one of those power machines. For example, some or all of the concepts discussed below can be practiced on many other types of work vehicles such as various other loaders, excavators, trenchers, and dozers, to name but a few examples.

The tractor 200 includes frame 210 that supports a power system 220, the power system being capable of generating or otherwise providing power for operating various functions on the power machine. Power system 220 is shown in block diagram form but is located within the frame 210 and not visible in FIG. 2 . Frame 210 also supports a work element in the form of a lift arm assembly 230 that is powered by the power system 220 and that can perform various work tasks. As tractor 200 is a work vehicle, frame 210 also supports a traction system 240, which is also powered by power system 220 and can propel the power machine over a support surface. The lift arm assembly 230 in turn supports an implement (e.g., accessory) interface 270 that can receive and secure various implements to the tractor 200 for performing various work tasks and power couplers 274 (see FIG. 4 ), to which an implement can be coupled for selectively providing power to an implement that might be connected to the loader. Power couplers 274 can provide sources of hydraulic or electric power or both.

The tractor 200 includes an operator station 255 from which an operator can manipulate various control devices 260 to cause the power machine to perform various work functions. The operator station 255 includes an operator seat 258 and a plurality of operation input devices, including control levers and a steering wheel (e.g., control devices 260) that an operator can manipulate to control various machine functions, such as steering functions, drive functions, and auxiliary hydraulic (i.e., pressurized hydraulic flow made selectively available to an operably coupled implement) functions. Operator input devices can include buttons, switches, levers, sliders, pedals and the like that can be stand-alone devices such as hand-operated levers or foot-operated pedals, incorporated into hand grips, or incorporated into display panels, which may be included on the dashboard 259, including programmable input devices. Actuation of operator input devices can generate signals in the form of electrical signals, hydraulic signals, or mechanical signals. Signals generated in response to operator input devices are provided to various components on the power machine for controlling various functions on the power machine. Among the functions that are controlled via operator input devices on tractor 200 include control of the tractive elements 219, the lift arm assembly 230, the implement interface 270, and providing signals to any implement that may be operably coupled to the implement.

The tractor 200 can include human-machine interfaces including display devices that are provided in the operator station 255 (e.g., on the dashboard 259) to give indications of information relatable to the operation of the power machines in a form that can be sensed by an operator, such as, for example audible or visual indications. Audible indications can be made in the form of buzzers, bells, and the like or via verbal communication. Visual indications can be made in the form of graphs, lights, icons, gauges, alphanumeric characters, and the like. Displays can provide dedicated indications, such as warning lights or gauges, or dynamic to provide programmable information, including programmable display devices such as monitors of various sizes and capabilities. Display devices can provide diagnostic information, troubleshooting information, instructional information, and various other types of information that assists an operator with operation of the power machine or an implement coupled to the power machine. Other information that may be useful for an operator can also be provided. Other power machines, such walk behind loaders may not have a cab nor an operator compartment, nor a seat. The operator position on such loaders is generally defined relative to a position where an operator is best suited to manipulate operator input devices.

Various power machines that can include or interacting with the examples discussed below can have various different frame components that support various work elements. The frame 210 discussed herein can include many elements, however the frame 210 is not the only type of frame that a power machine on which the disclosed technology can be practiced can employ. For example, the frame 210 of tractor 200 can include an undercarriage or lower portion of the frame 210 and a mainframe or upper portion of the frame 210 that is supported by the undercarriage. The mainframe of tractor 200, in some examples is attached to the undercarriage such as with fasteners or by welding the undercarriage to the mainframe. Alternatively, the mainframe and undercarriage can be integrally formed. The frame 210 also supports a pair of tractive elements in the form of wheels 219A-D on either side of the tractor 200.

The lift arm assembly 230 shown in FIG. 2 is one example of many different types of lift arm assemblies that can be attached to a power machine such as tractor 200 or other power machines on which examples of the present discussion can be practiced. The lift arm assembly 230 is moveable (i.e., the lift arm assembly can be raised and lowered) under control of the tractor 200 with respect to the frame 210 along a lift path 237. Other lift arm assemblies can have different geometries and can be coupled to the frame of a loader in various ways to provide lift paths. For example, some lift arm assemblies are configured to provide a vertical lift path, while others are configured to provide a radial lift path. Other lift arm assemblies can have an extendable or telescoping portion. Other power machines can have a plurality of lift arm assemblies attached to their frames, with each lift arm assembly being independent of the other(s). Unless specifically stated otherwise, none of the inventive concepts set forth in this discussion are limited by the type or number of lift arm assemblies that are coupled to a particular power machine.

The lift arm assembly 230 has a pair of lift arms 234 that are disposed on opposing sides of the frame 210. A first end of each of the lift arms 234 is pivotally coupled to the power machine and a second end of each of the lift arms 234 is positioned forward of the frame 210 as shown in FIG. 2 . In the illustrated example, the lift arms 234 are arranged proximate the front wheels 219A, 219C and, preferably, slightly forward of the front wheels 219A, 219C. The lift arms 234 are configured as forks. The lift arms 234 are preferably constructed of a relatively strong, stiff and durable material that is able to take on the general size and shape of the lift arms 234 and withstand the normal operating conditions of the lift arms 234. In a preferred example, the lift arms 234 may be constructed of a metallic material, such as steel, a composite material or nearly any relatively strong, stiff, and durable material. Lift arm assembly 230 is similar to what is commonly known as three point hitch assemblies. For the purposes of this discussion, it is referred to as a lift arm and in other examples, other configurations of lift arms can be employed.

The lift path 237 is defined by the path of travel of the second ends of the lift arms 234 as the lift arm assembly 230 is moved between a minimum and maximum height. A pair of actuators 238, which on tractor 200 are hydraulic cylinders configured to receive pressurized fluid from power system 220, are pivotally coupled to both the frame 210 and the lift arms 234 on either side of the tractor 200. The actuators 238 are sometimes referred to individually and collectively as lift cylinders. Actuation (i.e., extension and retraction) of the actuators 238 cause the lift arm assembly 230 to be raised and lowered along a fixed path generically illustrated by arrow 237.

Some lift arms, most notably lift arms on excavators but also possible on loaders, may have portions that are controllable to pivot with respect to another segment instead of moving in concert (i.e., along a pre-determined path). Some power machines have lift arm assemblies with a single lift arm, such as is known in excavators or even some loaders and other power machines. Other power machines can have a plurality of lift arm assemblies, each being independent of the other(s).

An implement interface 270 is provided proximal to the second ends of the lift arm assembly 230. The implement interface 270 is capable of accepting and securing a variety of different implements to the lift arm assembly 230. In the illustrated example, an implement configured as a mower deck 280 is mounted to the lift arms 234. Accordingly, the actuators 238 can be actuated to raise and lower the lift arms 234 and thereby raise and lower the mower deck 280 (e.g., for non-mowing travel and mowing travel, respectively). The implement is located generally forward of a front of the tractor 200 and may comprise any suitable accessory for the tractor 200. For example, the implement can be configured as a lawn mower deck (e.g., as shown), a snow blower, a trench digger, a sweeper, a plow, a dump bucket, a hole digger, a chipper, and an aerator, but is not so limited and may be nearly any variety of accessory that may be utilized and/or driven by the tractor 200. Generally, implements have a complementary machine interface that is configured to be engaged with the implement interface 270 to be mounted the lift arms 234 in an operational configuration. Locking features can also be provided to secure the implement to the lift arms 234 (e.g., an accessory locking hook and a locking pin to be captured by the locking hook).

The implement interface 270 also includes implement power couplers 274 (see FIG. 4 ) available for removably forming an operational power connection to an implement that can, but need to be, secured on the lift arm assembly 230. The implement power couplers 274 includes pressurized hydraulic fluid port to which an implement can be removably coupled. For example, the implement power couplers 274 can include hydraulic quick-disconnect couplers to provide hydraulic power to a removable hydraulic attachment. The pressurized hydraulic fluid port selectively provides pressurized hydraulic fluid for powering one or more functions or actuators on an implement. The implement power source can also include an electrical power source for powering electrical actuators or an electronic controller on an implement. The implement power couplers 274 also exemplarily includes electrical conduits that are in communication with a data bus on the tractor 200 to allow communication between user inputs on the tractor 200 (in some cases via a controller) and electrically powered actuators on an implement. For the purposes of this discussion, electric solenoid valves and electrically controlled servo actuators are included as electrically power actuators.

Frame 210 supports and generally encloses the power system 220 so that the various components of the power system 220 are not visible in FIG. 2 . FIG. 3 includes, among other things, a block diagram of various components of the power system 220. Power system 220 includes one or more power sources 222 that are capable of generating or storing power for use on various machine functions. On the tractor 200, the power system 220 includes an internal combustion engine. Other power machines can include electric generators, rechargeable batteries, various other power sources or any combination of power sources that can provide power for given power machine components. The power system 220 also includes a power conversion system 224, which is operably coupled to the power source 222. Power conversion system 224 is, in turn, coupled to one or more actuators 226, which can perform a function on the power machine. Power conversion systems in various power machines can include various components, including mechanical transmissions, hydraulic systems, and the like. The power conversion system 224 of the tractor 200 includes one or more hydrostatic drive pumps 224A, which are selectively controllable to provide a power signal to drive motors 226A-226D. According to the illustrated example, the power conversion system 224 can also include a charge pump 224B to provide a flow/pressure source for the activation of the controls for the hydrostatic drive pump 224A. The drive motors 226A-226D in turn are each operably coupled to axles, with drive motor 226A being coupled to axle 228A, drive motor 226B being coupled to axle 228B, and so on. The axles 228A-228D are in turn coupled to the wheels 219A-D, respectively. The drive pump(s) 224A can be mechanically, hydraulic, or electrically coupled to operator input devices to receive actuation signals for controlling the drive pumps. In the illustrated example, the tractor 200 is a four-wheel drive vehicle wherein the front and rear wheels 219A-219D provide driving force to move the tractor 200 along the ground. According to other examples, the tractor can be a two-wheel drive vehicle in which only the front wheels 219A, 219C or the rear wheels 219B, 219D provide the driving force. Alternatively still, the tractor can be a four wheel drive tractor with a single drive motor for the front axles and a single drive motor for the rear axles.

The arrangement of drive pump, motors, and axles in the tractor 200 is but one example of an arrangement of these components. As discussed above, the tractor 200 is a compact tractor, and thus tractive elements on each side of the power machine are controlled together via the output of a single hydraulic pump, either through a single drive motor, or with individual drive motors as in the tractor 200. Various other configurations and combinations of hydraulic drive pumps and motors can be employed as may be advantageous.

The power conversion system 224 of power machine 200 also includes an auxiliary hydraulic pump 224C, which is also operably coupled to the power source 222. The auxiliary hydraulic pump 224C is operably coupled to work actuator circuit 238C. Work actuator circuit 238C includes lift cylinders 238, steering actuators, auxiliary ports such as the power couplers 274, a load compensation system, as well as control logic to control actuation thereof. The control logic selectively allows, in response to operator inputs, for actuation of the lift cylinders. In some machines, the work actuator circuit 238C also includes control logic to selectively provide a pressurized hydraulic fluid to an operably coupled implement (e.g., via the power couplers 274).

The description of power machine 100 and tractor 200 above is provided for illustrative purposes, to provide illustrative environments on which the examples discussed below can be practiced. While the examples discussed can be practiced on a power machine such as is generally described by the power machine 100 shown in the block diagram of FIG. 1 and more particularly on a compact tractor such as the tractor 200, unless otherwise noted or recited, the concepts discussed below are not intended to be limited in their application to the environments specifically described above.

As previously described, the tractor 200 can include various control devices 260 that are manipulatable by an operator. Some control devices 260 are configured to be used to provide inputs to control the tractive elements 219. Referring to FIG. 4 , in the illustrated example, the tractor 200 includes a first drive input device 282 and a second drive input device 284. In one example, the first drive input device 282 is configured as a single-axis device (e.g., joystick or lever) to provide a first mode for controlling forward and reverse drive functions of the tractive elements 219. For example, moving the first drive input device 282 forward (or otherwise in a first direction relative to a particular degree of freedom) provides a control signal to control the drive motors 226A-226D (see FIG. 3 ) to power the tractive elements 219 to drive the tractor 200 in a forward direction. Conversely, moving the first drive input device 282 rearward (or otherwise in a second direction relative to the particular degree of freedom) provides a control signal to control the drive motors 226A-226D to power the tractive elements 219 to drive the tractor 200 in a rearward direction. As further discussed below, some control signals can control drive motors indirectly, including by controlling operation of a drive pump that provides hydrostatic power to the drive motors.

In one example, the second drive input device 284 is configured as two foot pedals, a forward foot pedal 284A and a reverse foot pedal 284B, to provide a second mode for controlling forward and reverse drive functions of the tractive elements 219. For example, actuation (e.g., depression) of the forward foot pedal 284A provides a control signal (e.g., a second control signal) to the drive motors 226A-226D to power the tractive elements 219 to drive the tractor 200 in a forward direction. Similarly, actuation of the reverse foot pedal 284B provides a control signal to the drive motors 226A-226D to power the tractive elements 219 to drive the tractor 200 in a rearward direction. In some examples, a forward foot pedal and a reverse foot pedal can be implemented independently, including with separate foot-engagement surfaces and separate pivoting attachments relative an operator station, as shown in the example of FIG. 4 . In some examples, forward and reverse pedals can be implemented in a combined device, including as a rocker pedal that can be pivoted in a first direction for forward commands and a second direction for rearward commands.

The first and second drive input devices 282, 284 can be moved independently of one another to provide multiple modes of control of the drive functions of the tractor 200, including when implemented as part of a hydraulic (e.g. pilot-controlled) system. FIG. 5 illustrates an example hydraulic control logic for the first and second drive input devices 282, 284 for an example hydraulic circuit, as can be used to control drive pump displacement and thereby control operation of one or more drive motors. In the illustrated example, the first and second drive input devices 282, 284 are operatively coupled to hydraulic control valves to selectively provide a control signal (e.g., pilot pressure) from the charge pump 224B to control the direction and output pressure of the drive pump 224A. The first drive input device 282 is operatively coupled to (e.g., includes) a forward joystick control valve 286A and a reverse joystick control valve 286B. Similarly, the forward foot pedal 284A of the second drive input device 284 is operatively coupled to (e.g., includes) a forward foot pedal control valve 288A and the reverse foot pedal 284B of the second drive input device 284 is operatively coupled to (e.g., includes) a reverse foot pedal control valve 288B. In some examples, as generally noted above, the foot pedals 284A, 284B and the valves 288A, 288B can sometimes be implemented as a single input assembly (e.g., a single rocker pedal assembly).

The forward outlet ports of the first and second drive input devices 282, 284 are arranged in parallel to provide a forward control signal for operation of the drive pump 224A and the reverse outlet ports of the first and second drive input devices 282, 284 are arranged in parallel to provide a reverse control signal for operation of the drive pump 224A. This arrangement allows an operator to utilize either or both of the first and second drive input devices 282, 284 to control the drive function of the tractor 200. In the illustrated example, coordinated control under this parallel arrangement is provided by two shuttle valves 290, including a first shuttle valve 290A arranged along a first flow path to provide forward control signals for the drive pump 224A and a second shuttle valve 290B arranged along a second flow path to provide reverse control signals for the drive pump 224A. As illustrated in FIG. 5 , the forward joystick control valve 286A and the forward foot pedal control valve 288A are in fluid communication with the first shuttle valve 290A, and the reverse joystick control valve 286B and the reverse foot pedal control valve 288B are in fluid communication with the second shuttle valve 290B.

During operation of the tractor 200, an operator can choose to independently utilize the first drive input device 282 (e.g., the joystick) or the second drive input device 284 (e.g., the foot pedals) to control the forward or reverse drive functions of the tractor 200, or to utilize the devices 282, 284 together (e.g., simultaneously). For example, if an operator desires to command the tractor 200 to move forward, the operator can move the first drive input device 282 in a forward direction, thereby engaging the forward joystick control valve 286A to provide a control signal using pilot control pressure from the charge pump 224B to the first shuttle valve 290A. Absent a countervailing pressure signal from the input device 284, as further discussed below, the pilot pressure will shift a shuttle element within the first shuttle valve 290A to allow the pilot pressure to be provided to a control mechanism 292 for the drive pump 224A and thereby adjust the displacement of the drive pump 224A. Similarly, the operator can depress the forward foot pedal 284A, thereby engaging the forward foot pedal control valve 288A to provide pilot pressure from the charge pump 224B to the first shuttle valve 290A. Absent a countervailing pressure signal from the input device 282, the pilot pressure will shift the shuttle element within the first shuttle valve 290A to allow the pilot pressure to be provided to the control mechanism 292 for the drive pump 224A. Regardless of the input device used, therefore, the pilot pressure provided through the first shuttle valve 290A can adjust the control mechanism 292 for the drive pump 224A to controllably provide pressure to the drive motors 226A-226D to drive the tractor 200, via the tractive elements 219 (see FIG. 4 ), in a forward direction.

According to another example, if an operator desires to command the tractor 200 to move in reverse, the operator can move the first drive input device 282 in a rearward direction, thereby engaging the reverse joystick control valve 286B to provide pilot pressure from the charge pump 224B to the second shuttle valve 290B. The pilot pressure will shift a shuttle element within the second shuttle valve 290B to allow the pilot pressure to be provided to the control mechanism 292 for the drive pump 224A. Alternatively, the operator can depress the reverse foot pedal 284B, thereby engaging the reverse foot pedal control valve 288B to provide pilot pressure from the charge pump 224B to the second shuttle valve 290B. The pilot pressure will shift the shuttle element within the second shuttle valve 290B to allow the pilot pressure to be provided to the control mechanism 292 for the drive pump 224A. In either case, the pilot pressure provided through the second shuttle valve 290B will adjust the control mechanism 292 for the drive pump 224A to provide pressure to the drive motors 226A-226D to drive the tractor 200, via the tractive elements 219, in a rearward direction.

Although the control mechanism 292 is shown as a spring-biased two-sided piston device in FIG. 5 , other examples can include other control devices that can control drive operations based on hydraulic pressure signals from operator input devices. Thus, for example, a similar hydraulic arrangement as is shown in FIG. 5 can be implemented in some cases with a differently configured hydraulic actuator to control operation of the drive pump 224A.

In some examples, the first and second drive input devices 282, 284 can provide proportional control (e.g., speed control) over the drive functions of the tractor 200. For example, the larger the input provided by the operator into the first and second drive input devices 282, 284, (whether hydraulic or electronic input devices) the larger the pilot pressure (or electronic signal) delivered to the control mechanism 292 for the drive motor 224A, and the larger the effect on the output pressure of the drive pump 224A to power the drive motors 226A-226D. Further, when an operator is engaging each of the first and second drive input devices 282, 284 to command movement the tractor 200 in a forward direction or in a reverse direction, the shuttle valves 290A, 290B operate to ensure that the larger magnitude of the two same-direction inputs from the first drive input device and the second drive input device 284 will dominate (e.g., define) the command signal to the control mechanism 292. The same can hold true for input devices that are electronic.

In some implementations, an operator can also utilize a first-direction command at one of the first and second drive input devices 282, 284 to effectively derate the control signal provided by the other of the first and second drive input devices 282, 284. For example, based on a first operator input, the first drive input device 282 can provide a first control signal at a first magnitude corresponding to a position of the first drive input device 282 (e.g., the joystick at a maximum forward position). Simultaneously, based on a second operator input, the second drive input 284 device can provide an opposing second control signal at a second magnitude corresponding to a position of the second drive input device 284 (e.g., the reverse foot pedal 284B at a position between an undepressed and fully depressed position). In this case, each of the first and second control signals will be provided from the first and second shuttle valves 290A and 290B, respectively, as opposing pilot signals at to the control mechanism 292. These opposing, yet unequal control signals will adjust the control mechanism to be biased towards the larger of the first and second magnitudes. For example, with the joystick at a maximum forward position and the reverse foot pedal 284B at a position between an undepressed and fully depressed position, the control mechanism 292 will be moved to a setting that is lower than a maximum forward setting, owing to the derating effect provided by the partial depression of the reverse foot pedal 284B. Thus, in some implementations, finer and more adaptable operator control can be provided, including via the ability to regulate forward commands at one input device using rearward commands at another device (or vice versa). For example, during extended travel an operator may rest passively to hold a joystick at a maximum forward command, then effectively reduce the forward command as desired via selective rearward inputs at a foot pedal.

Referring to FIGS. 6 and 7 , the tractor 200 of FIG. 4 can include control devices 260 configured to be used to provide inputs to control power machine work elements, including actuators 238 (e.g., a lift cylinder), and one or more implement functions (e.g., via control of one or more tilt cylinders (not shown)). In the illustrated example, the tractor 200 includes an implement input device 300 that includes a dual axis joystick 301 (see FIG. 6 ) for control of a first work element (e.g., the actuator 238) and a second work element (e.g., an implement actuator) by way of a connection through the power couplers 274.

With reference to FIG. 7 in particular, in the illustrated example, the work actuator circuit 238C is configured to received pressurized fluid from the auxiliary pump 224C. The implement input device 300 is operatively coupled to a first hydraulic control spool 302A and a second hydraulic control spool 302B to selectively control the delivery of the pressurized fluid to the first and second work elements. Movement of the joystick 301 along a first axis 306 (e.g., movement in a forward and backward direction, as shown in FIG. 6 ) controls the position of the first hydraulic control spool 302A, which in turn controls the actuation of the actuator 238. Similarly, movement of the joystick 301 along a second axis 308 (e.g., movement in a side-to-side lateral direction, as shown in FIG. 6 ) controls the position of the second hydraulic control spool 302B, which in turn controls the actuation of an actuator or work element connected to the tractor 200 through the power couplers 274. Thus, in some examples, movement of the joystick 301 along different axes can control different work functions of the power machine, including lift functions and auxiliary functions in some cases.

Power machines of the type described herein can be operably coupled to and selectively provide pressurized hydraulic fluid (or electrical power) to control one or more actuators on various implements. For example, in some implementations, movement of the joystick 301 along the first axis can control extension and retraction of a lift cylinder for a lift arm to which an implement is operably coupled (e.g., to raise and lower a mower deck attachment) and movement of the joystick 301 along the second axis can control operation of a motor or other powered device of the implement (e.g., to power rotary cutting on a mower). As another example, movement of the joystick 301 along the first axis can control extension and retraction of a lift cylinder (e.g., to raise and lower a lift arm structure) and movement of the joystick 301 along the second axis can control operation of a tilt cylinder (e.g., to change an attitude of an implement with respect to the lift arm structure). These representative applications are provided to highlight the types of functions on an implement that can be controlled by side-to-side movement of the joystick 301 in the interest of brevity. Other functions on other implements can be controlled in a similar manner.

As illustrated in FIG. 7 , the first and second hydraulic control spools 302A, 302B include a respective float position 304A, 304B. The float positions 304A, 304B are provided to open both sides of the work element control circuit to tank and thereby allow one or more associated actuators to move freely under external loads (i.e., without powered hydraulic resistance to the movement). For example, when the first hydraulic control spool 302A is in the float position 304A, the extend side and the retract side of the lift actuator 238 are in fluid communication with tank. This can allow the lift actuator 238 to be moved by contact between the implement (e.g., a mower deck) and a ground surface so that the implement can easily follow contours of the surface without active intervention from the lift actuator 238 to control the lifted height of the implement. Similarly, when the second hydraulic control spool 302B is in the float position 304B, the extend side and the retract side of the power couplers 274 (e.g., coupled to a tilt cylinder on an implement) are in fluid communication with tank, such that an implement operably coupled to the power couplers 274 may operate in an equivalent float configuration. As discussed above, there are various types of implements that can be operably coupled to power machines of the type discussed herein. As such, this implement float feature can be made available for various operations, including allowing float for various types of actuators (e.g., linear, rotary) for tilt or other actuation for an implement.

In the illustrated example, the float positions 304A, 304B are activated when the first and second hydraulic control spools 302A, 302B are shifted to a maximum end position, as results from the joystick 301 being positioned in a maximum end position. For example, movement of the joystick 301 to a forwardmost position along the first axis 306 positions the first hydraulic control spool 302A in the float position 304A. Similarly, movement of the joystick 301 to a leftmost lateral position along the second axis 308 positions the second hydraulic control spool 302B in the float position 304B. In other examples, other methods can be used to signal an operator's intent to move one or more of the spools discussed herein (or other arrangements) into a float position.

In some implementations, the implement input device 300 is configured to maintain the first hydraulic control spool 302A in the float position 304A during movement of the joystick 301 along the second axis 308. For example, due to the dual-axis configuration of the joystick 301, an operator can position the joystick 301 to a forward most position along the first axis 306 to place the lift actuator 238 in a float configuration. While the joystick 301 is in the forward most position, an operator can move the joystick 301 laterally to operate an auxiliary function of an implement (e.g., a tilt function), while the joystick still maintains the first hydraulic control spool 302A in the float position 304A. In some examples, only one of axes of joystick 301 can be put into a float condition at any given time, and any movement of the joystick along either axis can result in the end of a float condition. Again, one of ordinary skill in the art will understand that various examples can employ different user inputs to command float in either (or both) spools 302A, 302B.

In some examples, for example, the first hydraulic control spool 302A can be maintained in the float position 304A over a sufficient range of lateral movement of the joystick 301 to also place the auxiliary function in a float configuration (e.g., to a leftmost position). In that way, for example, the joystick 301 can place two hydraulic functions into a float configuration or maintain a first hydraulic function in a float configuration while simultaneously actively operating a second hydraulic function. Further, in some examples, similar functionality can also (or alternatively) be implemented to maintain a float configuration for the second hydraulic function during active operation of the first hydraulic function.

In some examples, a hydraulic control system can be configured to provide a float assist mode of operation for one or more hydraulic functions. For example, an electronic or other switch can be configured to actuate an electronic or other control valve to controllably connect a hydraulic actuator to a pressurized flow to resist, but not stop, movement of the actuator under external loads. In some examples, a joystick assembly can be configured to automatically actuate a relevant switch once a joystick is moved to a particular position. In some examples, other arrangements of input devices can be similarly employed (e.g., with a manually-actuated switch to implement float assist).

In some examples, a joystick assembly can be configured to engage a float assist switch based on a threshold movement of a joystick along a first axis and to thereafter maintain engagement with the float assist switch over a range of positions along a second axis. In some examples, a joystick assembly can include a switch and a manufactured bracket arranged to activate the switch when a joystick is moved to a first position in a first direction, and to maintain the activation along a range of positions of the joystick in a transverse second direction. Such a bracket, for example, can be implemented as a retrofit kit for preexisting systems in some cases.

In one example, as illustrated in FIG. 6 , the implement input device 300 can include a bracket 310 coupled to a base of the joystick 301. The bracket 310 is configured to engage a switch 312 to activate an implement load compensation system 314 (see FIG. 7 ), including as can implement a float assist mode for one or more work functions.

In the illustrated example, the implement load compensation system 314 is configured to apply a set pressure to the lift actuator 238 to reduce the ground pressure from the implement (e.g., thereby improving the weight distribution on the tractive elements 219 of the tractor 200). In general, implements (e.g., mower decks) attached to tractors can be heavy, resulting in a change of the weight distribution on the tractive elements of the tractors (e.g., shifting weight or moving the center of gravity of the tractor toward the front of the tractor 200). The change in weight distribution can affect the traction provided by the tractive elements and can be particularly pronounced when the tractor is traversing a slope, including during float operation (e.g., with the hydraulic control spools 302A, 302B in a float position).

With continued reference to FIGS. 6 and 7 , the implement load compensation system 314 includes first and second solenoid-operated control valves 316A, 316B and an adjustable pressure relief valve 318. Actuation of the switch 312 provides a command signal to the first and second solenoid-operated control valves 316A, 316B, which transitions the lift actuator 238 from being in a float configuration, by way of the float position 304A of the first hydraulic control spool 312A, to being in a load-compensated (e.g., float assist mode) configuration, as controlled by the adjustable pressure relief valve 318. In the load-compensated configuration, a first side (e.g., a retract or lift side) of the lift actuator 238 is placed in fluid communication with the pressure relief valve 318 and a second side (e.g., a lower or extend side) of the lift actuator 238 is placed in fluid communication with tank. An operator can control the amount of load compensation by adjusting a control device 260 (e.g., a knob 320, see FIG. 4 ), which adjusts a pressure setting of the pressure relief valve 318. By increasing the pressure setting, more pressure is delivered to the lift actuator 238 by the auxiliary pump 224C to reduce the ground pressure of the implement. Further, with sufficient low upper pressure limits provided by the pressure relief valve 318, floating movement of the lift actuator 238 can be maintained with pressure from the auxiliary pump 224C resisting but not stopping movement of the lift actuator 238 under external loads (e.g., the gravitational load from the mass of the lift arm).

Referring to FIG. 6 in particular, the bracket 310 is contoured such that a central portion 322 of the bracket 310 actuates the switch 312 when the joystick 301 is positioned to the forwardmost position along the first axis 306, which corresponds to the float position 304A (see FIG. 7 ). Further, in the illustrated example, the bracket 310 includes lateral extensions (e.g., flanges 324A, 324B, as shown) extending away from the central portion 322 of the bracket 310 in a direction along the second axis 308. The flanges 324 are angled with respect to the central portion 322 to provide a combined surface that maintains contact with the switch 312 during lateral movement of the joystick 301 along the second axis 308 while the joystick 301 remains positioned in the forwardmost position. In that way, an operator can move the joystick laterally to operate an auxiliary function of an implement (e.g., a tilt function), including positioning the joystick 301 in a leftmost position to place the auxiliary function in a float configuration, while the implement load compensation system 314 remains activated.

Although the presently disclosed technology has been described by referring preferred examples, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the discussion.

As used herein in the context of a power machine, unless otherwise defined or limited, the term “lateral” refers to a direction that extends at least partly to a left or a right side of a front-to-back reference line defined by the power machine. Accordingly, for example, a lateral side wall of a cab of a power machine can be a left side wall or a right side wall of the cab, relative to a frame of reference of an operator who is within the cab and is oriented to operatively engage with controls of an operator station of the cab.

Also as used herein, unless otherwise limited or defined, “or” indicates a non-exclusive list of components or operations that can be present in any variety of combinations, rather than an exclusive list of components that can be present only as alternatives to each other. For example, a list of “A, B, or C” indicates options of: A; B; C; A and B; A and C; B and C; and A, B, and C. Correspondingly, the term “or” as used herein is intended to indicate exclusive alternatives only when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” For example, a list of “one of A, B, or C” indicates options of: A, but not B and C; B, but not A and C; and C, but not A and B. A list preceded by “one or more” (and variations thereon) and including “or” to separate listed elements indicates options of one or more of any or all of the listed elements. For example, the phrases “one or more of A, B, or C” and “at least one of A, B, or C” indicate options of: one or more A; one or more B; one or more C; one or more A and one or more B; one or more B and one or more C; one or more A and one or more C; and one or more of A, one or more of B, and one or more of C. Similarly, a list preceded by “a plurality of” (and variations thereon) and including “or” to separate listed elements indicates options of multiple instances of any or all of the listed elements. For example, the phrases “a plurality of A, B, or C” and “two or more of A, B, or C” indicate options of: A and B; B and C; A and C; and A, B, and C.

In some implementations, devices or systems disclosed herein can be utilized, manufactured, installed, etc. using methods embodying aspects of the disclosed technology. Correspondingly, any description herein of particular features, capabilities, or intended purposes of a device or system is generally intended to include disclosure of a method of using such devices for the intended purposes, of a method of otherwise implementing such capabilities, of a method of manufacturing relevant components of such a device or system (or the device or system as a whole), and of a method of installing disclosed (or otherwise known) components to support such purposes or capabilities. Similarly, unless otherwise indicated or limited, discussion herein of any method of manufacturing or using for a particular device or system, including installing the device or system, is intended to inherently include disclosure, as examples of the disclosed technology, of the utilized features and implemented capabilities of such device or system.

As used herein in the context of electronic control systems, unless otherwise specified or limited, the term “module” is intended to encompass generally known hardware devices, software tools, and combinations thereof for electronic control systems that can be configured or customized to implement particular functionality. For example, a module may include a variety of known circuitry or electrical components that can be configured for controlled powered operation of actuators, including general or special purpose processor devices, motor drives, field programmable devices, executable instructions on computer readable media, and so on. 

What is claimed is:
 1. A power machine comprising: a power source; drive motors operably coupled to the power source and to tractive elements of the power machine to power drive operations of the power machine; a first drive input device configured to provide a first control signal to selectively power operation of the drive motors for travel in a forward direction or a reverse direction; and a second drive input device configured to provide a second control signal to selectively power operation of the drive motors for travel in the forward or the reverse direction; wherein the first drive input device is independently movable relative to the second drive input device to provide the first control signal and the second drive input device is independently movable relative to the first drive input device to provide the second control signal.
 2. The power machine of claim 1, further comprising: a drive pump operably coupled to the power source and configured to power the drive motors to selectively drive the power machine in the forward direction or the reverse direction; wherein the drive motors are hydraulically powered drive motors; and wherein the first drive input device is configured to provide the first control signal to control the drive pump to selectively power operation of the drive motors for travel in the forward direction or the reverse direction; and wherein the second drive input device is configured to provide the second control signal to control the drive pump to selectively power operation of the drive motors for travel in the forward or the reverse direction.
 3. The power machine of claim 1, wherein the first drive input device includes a single-axis joystick.
 4. The power machine of claim 1, wherein the second drive input device includes at least one foot pedal.
 5. The power machine of claim 1, wherein the first drive input device and the second drive input device are in hydraulic communication with a hydraulically operated control device arranged to provide pilot-operated control of displacement of a drive pump using hydraulic pressure within a drive control hydraulic circuit; wherein the drive control hydraulic circuit includes a first control path that includes a first shuttle valve between the hydraulically operated control device and a first outlet port of each of the first and second drive input devices, with first inlets of the first shuttle valve in hydraulic communication with the first outlet ports, and with a first outlet of the first shuttle valve in hydraulic communication with the hydraulically operated control device to provide a first pilot control signal to the hydraulically operated control device; and wherein the drive control hydraulic circuit includes a second control path that includes a second shuttle valve between the hydraulically operated control device and a second outlet port of each of the first and second drive input devices, with second inlets of the second shuttle valve in hydraulic communication with the second outlet ports, and with a second outlet of the second shuttle valve in hydraulic communication with the hydraulically operated control device to provide a second pilot control signal to the hydraulically operated control device opposed to the first pilot control signal.
 6. A hydraulic control circuit for a drive system of a power machine, the hydraulic control circuit comprising: a first drive input device in communication with a pilot pressure source and configured to receive a first operator input relative to a first degree of freedom and to selectively provide, based on the first operator input, a first pilot signal along first control path or along a second control path to command, respectively, operation of a drive motor of the drive system in a forward direction or a reverse direction; a second drive input device in communication with a pilot pressure source and configured to receive a second operator input relative to a second degree of freedom and to selectively provide, based on the second operator input, a second pilot signal along the first control path or along the second control path to command, respectively, operation of the drive motor of the drive system in the forward direction or the reverse direction; a pilot-operated actuator configured to control a displacement of the drive motor based on pilot signals from the first and second control paths; a first shuttle valve arranged along the first control path between the pilot-operated actuator and the first and second drive input devices; and a second shuttle valve arranged along the second control path between the pilot-operated actuator and the first and second drive input devices.
 7. The hydraulic control circuit of claim 6, wherein the first drive input device includes a joystick and the second drive input device includes a pedal.
 8. A power machine comprising: a power source; a work element configured to be powered by the power source for work operations; an implement interface configured to removably, operably couple an implement to the power machine; at least one power coupler configured to transmit power from the power machine to the implement when the implement is removably, operably coupled to the implement interface; and a dual-axis joystick; wherein movement of the dual-axis joystick along a first axis actuates a first actuator configured for a first work function; wherein movement of the dual-axis joystick along a second axis actuates a second actuator of the implement that is powered via the at least one power coupler for a second work function of the implement; wherein the dual-axis joystick being positioned at a first threshold position along the first axis places the first actuator in a float configuration for the first work function; and wherein the dual-axis joystick being positioned at a second threshold position along the second axis places the second actuator in a float configuration for the second work function.
 9. The power machine of claim 8, further comprising: an auxiliary pump operably coupled to the power source and configured to pressurize a work actuator circuit that includes the first actuator; wherein the at least one power coupler is configured to place the implement in fluid communication with the work actuator circuit to transmit hydraulic power from the power machine to the implement; wherein the dual-axis joystick is operably coupled to a first hydraulic control spool and a second hydraulic control spool; wherein movement of the dual-axis joystick along the first axis adjusts a position of the first hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to actuate the first actuator; wherein movement of the dual-axis joystick along the second axis adjusts a position of the second hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to the at least one power coupler for actuation of the second actuator; wherein, when the dual-axis joystick is positioned at the first threshold position along the first axis, the first hydraulic control spool is positioned to place the first actuator in the float configuration for the first work function; and wherein, when the dual-axis joystick is positioned at the second threshold position along the second axis, the second hydraulic control spool is positioned to place the second actuator in the float configuration for the second work function.
 10. The power machine of claim 9, further comprising: a switch in communication with a control system of the power machine, the switch arranged to be actuated by movement of the dual-axis joystick to a third threshold position along the first axis; wherein, upon actuation of the switch, the control system is configured to implement a float assist mode in which the auxiliary pump provides pressurized flow in the work actuator circuit to resist but not stop movement of the first actuator under external loads.
 11. The power machine of claim 10, wherein the first threshold position is different from the second threshold position.
 12. The power machine of claim 10, further comprising: a first solenoid valve arranged on a first side of the first actuator and a second solenoid valve on a second side of the first actuator; wherein actuation of the switch commands control of the first and second solenoid valves to implement the float assist mode; and wherein the first and second solenoid valves are configured to remove the first actuator from fluid communication with the first hydraulic control spool.
 13. The power machine of claim 12, wherein, when the switch is actuated, the first solenoid valve places the first side of the first actuator in fluid communication with an adjustable pressure relief valve configured to adjust a pressure delivered to the first side of the first actuator by the auxiliary pump.
 14. The power machine of claim 8, further comprising: a bracket coupled to the dual-axis joystick and configured to engage a switch to implement a float assist mode when the dual-axis joystick is positioned at a maximum end position along the first axis, across a range of positions along the second axis.
 15. The power machine of claim 14, wherein the bracket extends along the second axis such that the bracket maintains contact with the switch during movement of the dual-axis joystick along the second axis within the range of positions along the second axis.
 16. A power machine assembly comprising: the power machine according to claim 8; and the implement, operably coupled to the implement interface of the power machine and to the at least one power coupler.
 17. A power machine comprising: a power source; a hydraulic pump operably coupled to the power source and configured to pressurize a work actuator circuit; a work element configured to be powered by the hydraulic pump for work operations; a dual-axis joystick; and a switch in communication with a control system of the power machine; wherein movement of the dual-axis joystick along a first axis selectively provides pressurized fluid from the hydraulic pump to actuate a first actuator configured for a first work function; wherein movement of the dual-axis joystick along a second axis selectively provides pressurized fluid from the hydraulic pump to actuate a second actuator configured for a second work function; wherein, when the dual-axis joystick is positioned at a first threshold position along the first axis, the dual-axis joystick actuates the switch to place the first actuator in a float configuration for the first work function; and wherein, upon actuation of the switch, the control system is configured to implement a float assist mode in which the hydraulic pump provides pressurized flow in the work actuator circuit to resist but not stop movement of the first actuator under external loads.
 18. The power machine of claim 17, wherein the dual-axis joystick is operably coupled to a first hydraulic control spool and a second hydraulic control spool; wherein movement of the dual-axis joystick along the first axis adjusts a position of the first hydraulic control spool to selectively actuate the first actuator; wherein movement of the dual-axis joystick along the second axis adjusts a position of the second hydraulic control spool to selectively actuate the second actuator; and wherein, when the dual-axis joystick is positioned at the first threshold position along the first axis, the dual-axis joystick positions the first hydraulic control spool to place the first actuator in the float configuration.
 19. The power machine of claim 17, wherein the hydraulic pump is an auxiliary pump.
 20. A power machine comprising: an implement interface configured for operably coupling a removable implement to the power machine; a work element; a power source; an auxiliary pump operably coupled to the power source and configured to pressurize a work actuator circuit, the work actuator circuit including: a first actuator arranged to be powered by the auxiliary pump to power work operations with the work element; and at least one power coupler configured to selectively provide pressurized fluid to the removable implement when the removable implement is operably coupled to the at least one power coupler; and a dual-axis joystick operably coupled to a first hydraulic control spool and a second hydraulic control spool; wherein movement of the dual-axis joystick along a first axis adjusts a position of the first hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to actuate the first actuator; wherein movement of the dual-axis joystick along a second axis adjusts a position of the second hydraulic control spool to selectively provide pressurized fluid from the auxiliary pump to the at least one power coupler for actuation of a second actuator arranged on the removable implement. 